Thermoplastic resins have a lower specific gravity than glass or metal and can have excellent mechanical physical properties such as excellent moldability and impact resistance. Plastic products made using such thermoplastic resins are quickly replacing conventional glass and metal products in fields such as electric and electronic products and automobile components.
Recently, there is a growing demand by users for an environmentally-friendly non-painted resin, as well as a growing demand by users for a metallic resin with a metallic like appearance imparted thereto by the resin itself without a coating process. Also, materials with low gloss or no gloss are increasingly being used in plastic materials for interior and exterior automobile components, in order to provide a luxurious appearance and touch.
A metallic appearance can be imparted to a resin without a coating process by adding metal particles to a resin composition. However, there can be appearance problems caused by flow-marks or weld-lines caused by the metal particles after an injection molding. Also, a mold should be additionally changed or the application is limited.
In order to solve these problems, Korean patent laid-open publication No. 2013-0078747 discusses controlling the shape or the aspect ratio of a metal particle. Also there is research directed to improving a surface coating material for a metal particle. However, even though these can provide some improvements, there also can be a limit on improving appearance problems, such as flow-marks or weld-lines caused by non-uniformity, agglomeration, and/or orientation of metal particles after an injection molding.
In addition, there are methods using rubber polymer particles having a large particle size or a matting agent to control the degree of gloss of a material itself. When the degree of gloss is controlled only with the rubber polymer particle having a large particle size, a large amount of the rubber polymer particles should be used to provide sufficient matting effect. The increased amount of rubber polymer, however, can decrease heat resistance, hardness, and/or light resistance.
When the amount of a matting agent is increased to provide a sufficient matting effect, impact resistance, flowability, and the like can be sharply reduced. In addition, although the matting effect itself can be excellent, appearance can be irregular.
Therefore, in order to resolve the aforementioned problems, there is a growing need to develop a thermoplastic resin composition providing excellent appearance with minimal or no deterioration of physical properties such as impact resistance and the like, by controlling the degree of gloss and the shielding ability of a material itself.